Comprehensive Study on Newly Developed Diffusion-Desorption Models Based on Knudsen and Langmuir Models in Tight Gas Reservoirs

Fluid flow in unconventional porous media is extremely complex due to the many physical processes and forces that governs fluid flow, such as diffusion, inertia, viscous flow, and sorption. Furthermore, modeling fluid flow in poor porous media often disregards the mentioned forces, assuming viscous transport is the predominant controller. This work introduces a new comprehensive flow model suitable for tight unconventional reservoirs, including viscous, inertia, diffusion, and sorption forces, to account for fluid transport in the three scales. The new model addresses 1-D linear flow in tight unconventional reservoirs and has been mathematically derived and numerically solved using MATLAB software and tested against a synthetic case study. The new models have been numerically solved and analyzed using synthetic data with previously published models that cater to the same phenomena and analyzed. In addition to studying the flow regimes effecting gas flow in porous media. It has been observed that the diffusion system becomes more prominent in regulating flow velocity with low permeability of the formation rock and low viscosity of the flowing fluid. Additionally, as a result, the sorption mechanism contribution to the flow increases with low permeability of the medium and low viscosity of the flowing fluid as it affects the concentration of gas, leading to release gas from being trapped in pores and rock surfaces.